Absorption refrigeration machine

ABSTRACT

An aqua-ammonia absorption refrigeration system employing an ammonia sensor in the chilled water circuit to detect the presence of ammonia therein and shut down the system to prevent serious corrosion of the chilled water circuit by ammonia.

United States Patent Earl L. Brown Brownlburg, Ind. 820,938

May 1,1969

June 22, 1971 Carrier Corporation Syracuse, N.Y.

Inventor Appl. No. Filed Patented Assignee ABSORPTION REFRIGERATION MACHINE 4 Claims, 2 Drawing Fip. us. 62/126, 62/148, 62/476, 165/11, ZOO/61.03 1m. c1 ..F25b 15/04, HOlh 35/24 mu olsflldi 62/125,

126,129,141, 476; 73/86, 148; 165/11, 70; ZOO/61.03, 61.04, 61.08

[56] References Cited UNITED STATES PATENTS 1,780,483 11/1930 Havens,Jr. ZOO/61.03 3,122,001 2/1964 Pritchettetal... 62Il26 3,222,920 12/1965 Marshetal. 73/86 Primary Examiner-William F. O'Dea Assistant Examiner-P. D. Ferguson Attorneys-Harry G. Martin, Jr. and J. Raymond Curtin ABSTRACT: An aqua-ammonia absorption refrigeration system employing an ammonia sensor in the chilled water circuit to detect the presence of ammonia therein and shut down the system to prevent serious corrosion of the chilled water circuit by ammonia.

Yji31585.809

PATENTEU JUN22 l97l q wf IIIIII INVENTOR.

V// I I w ammmi EARL L] BROWN BY v ATTORNEY.

ABSORPTION REFRIGERATION MACHINE BACKGROUND OF THE INVENTION In aqua-ammonia refrigeration machines used for air conditioning, a coil for direct expansion of refrigerant to cool the air within the conditioned space can not be utilized due to the possibility of a leak in the coil or associated tubing and the poisonous nature of ammonia which could escape into the conditioned space. The machine may therefore be used to chill water or a suitable antifreeze solution which is supplied to the conditioned space for cooling the air therein. However, if a leak should occur in the ammonia-chilled water heat exchanger, ammonia could be circulated through the chilled water circuit. Since the chilled water circuit is ordinarily fabricated from copper which readily corrodes in the presence of ammonia, there still exists a remote possibility of introducing ammonia into the conditioned space through an opening in the chilled water circuit created by this corrosion. Irrespective of the ammonia danger, unless the ammonia leak into the chilled water circuit is detected very early, .the circuit would be badly corroded and replacement thereof would be necessa- SUMMARY OF THE INVENTION The present invention relates to an aqua-ammonia refrigeration system employing an ammonia sensor in the chilled water circuit of the system. Means are provided for stressing a piece of brass which is associated with the electrical control circuit of the system. The stressed brass maintains a closed circuit unless it is corroded by ammonia and fails, thereby opening the electrical circuit and shutting down the system.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram of an absorption refrigeration system; and

FIG. 2 is an enlarged sectional view of the ammonia sensor employed with the refrigeration system.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, there is shown a refrigeration system comprising an absorber 10, a condenser 12, an evaporator or chiller 14, a generator 16, a liquid-suction heat exchanger 18, and a vapor distributor 20, connected to provide refrigeration. A pump 22 actuated by pump motor 23 is employed to circulate weak absorbent solution from absorber to generator 16.

As used herein, the term weak absorbent solution refers to solution which is weak in absorbent power, and the term strong absorbent solution" refers to a solution which is strong in absorbent power. A suitable absorbent for use in the system described is water; a suitable refrigerant is ammonia.

Liquid refrigerant condensed in condenser 12 passes through refrigerant liquid passage 24 to the liquid-suction heat exchanger. The liquid-suction heat exchanger 18 includes a housing 26 having a refrigerant restrictor 28 at the upstream end and a refrigerant restrictor 30 at the downstream end thereof. A portion of the liquid refrigerant supplied to the liquid-suction heat exchanger 18 flashes upon passing through restrictor 28 due to the low pressure existing downstream of the restrictor, thereby cooling the remainder of the refrigerant in the housing 26. The cooled refrigerant liquid and flashed refrigerant vapor then pass through restrictor 30 into heat exchanger 32 of chiller 14.

A heat exchange medium suchas water is passed over the exterior of heat exchanger 32 where it is chilled by giving up heat to evaporate the refrigerant within the heat exchanger. The chilled heat exchange medium passes out of chiller 14 through line 34 to suitable remote heat exchangers (not shown) after which it is returned to the chiller through inlet 36 for rechilling.

An ammonia sensor 31 as illustrated in FIG. 2 is disposed in the air space of the chiller and operably connected to the electrical circuit of the machine. The sensor 31 is comprised of a housing 33 having a cylindrically extending wall 35, passageways 37 and a recess 39 formed therein. A button 41 having a slot 43 formed therein and a spring 45 are disposed in recess 39. A brass wire 47, which is attached to electrical leads 49 by crimp connectors 51 or other suitable means, is routed through passageways 37 and slot 43. The sensor is assembled by tensioning leads 49 so that spring 45 and brass wire 47 are stressed. Potting material 53 such as epoxy is then utilized to fill passageways 37 and hold wire 47 within the passageways so that wire 47 is permanently stressed by spring 45.

By way of illustration, a suitable control circuit, including gas valve 75, pump motor 23, absorber-condenser fan motor 55, transformer 57, relay 59, room thermostat 61, and ammonia sensor 31 is provided to control the machine. When the thermostat 61 closes in response to room temperature, the circuit including sensor 31, relay 59, and gas valve 75 is completed. The relay 59 in turn completes the circuit including fan motor 55 and pump motor 23. In the event there is an ammonia leak in the chiller 14, the ammonia will rapidly corrode stressed brass wire 47 causing it to break and open the control circuit. This will immediately shut off the machine to prevent passage of ammonia water into the copper-chilled water circuit. It should be understood that this circuit is merely schematic and that a number of safety controls such as hightemperature limit switches, motor-overload switches, etc. may also be employed in the circuit.

The cold refrigerant evaporated in heat exchanger 32, along with a small quantity of absorbent which is carried over to the chiller with the refrigerant from the generator, passes into refrigerant vapor passage 38 of liquid-suction heat exchanger 18. The refrigerant vapor and absorbent liquid, which has a large quantity of refrigerant absorbed therein, passes through refrigerant vapor passage 38 in heat exchange relation with the refrigerant passing through housing 26. Refrigerant vapor passage 38 is provided with a turbulator 40 which consists of a twisted metal strip to provide a tortuous flow path for the vapor to provide optimum heat transfer between the vapor and liquid in passage 38 and the liquid refrigerant in housing 26. By passing the vapor and liquid in passage 38 in heat transfer with the liquid refrigerant in housing 26, a large quantity of refrigerant in the absorbent liquid in passage 38 is vaporized. The heat of vaporization is therefore removed from the liquid in housing 26, thereby reducing the temperature of the liquid refrigerant supplied to heat exchanger 32. This heat transfer within the liquid-suction heat exchanger 18 provides an increase in the absorption machine efficiency by transfern'ng heat from the liquid supplied thereto from the condenser to the refrigerant vapor and absorbent liquid discharged from the chiller.

Refrigerant vapor and absorbent solution from passage 38 is supplied to refrigerant distributor 20 through line 42. Strong solution, which is supplied from the generator to distributor 20 through line 52 mixes with the vapor and solution supplied to the distributor through line 42. The refrigerant vapor-absorbent solution mixture from distributor 20 is supplied to individual circuits $8 of the absorber 10 through absorber supply tubes 56. Suitable fan means, including motor 55, are provided for passing ambient air over the surface of the absorber in heat exchange relation with the solution therein for cooling the absorbent solution to promote the absorption of the refrigerant vapor by the solution. The same cooling medium may be supplied to condenser 12 in heat exchange relation with refrigerant vapor therein to condense the refrigerant.

Cold weak absorbent solution passes from absorber 10 through line 61 into pump 22. Liquid from pump 22 is passed through line 63 to rectifier heat exchange coil 64. The weak solution passes through coil 64 in heat exchange relation with hot strong solution passing through heat exchange coil 66 disposed within coil 64 and with the hot refrigerant vapor flowing through rectifier shell 68 in contact with the outer surface of coil 64. The weak solution from coil 64 is discharged into the upper portion of generator 16 along with any vapor which is formed in coil 64 due to heatexchange with the hot vapor passing thereover and the hot solution flowing therethrough.

Generator 16 comprises a shell 70 having tapered fins 72 suitably affixed thereto as by welding. Suitable heating means, including gas b'umer 74 and gas valve 75, are provided for heating the generator. The weak solution is boiled in generator 16 to concentrate the solution, thereby forming a strong solution and refrigerant vapor.

The hot strong absorbent solution passes upwardly through the analyzer section of generator 16 through analyzer coil 76 in heat exchange with the weak solution passing downwardly over the coil. The warm strong solution then passes through heat exchange coil 66 within coil 64 and line 52 into the distributor 20. A restrictor 78 is provided in line 52 so that the solution supplied to the vapor distributor 20 is at the same pressure as the vapor in line 42.

Refrigerant vapor formed in generator 16 passes upwardly through the analyzer section thereof where it is concentrated by mass heat transfer with weak solution passing downwardly over analyzer coil 76. Analyzer plates 80 in generator 16 provide a tortuous path for flow of solution and vapor to assure intimate contact therebetween to improve the mass heat transfer. The vapor then passes through rectifier 68 in heat exchange relation with the weak solution passing through coil 64. Absorbent condensed in rectifier 68 flows downwardly into the generator along with the weak solution discharged from coil 64. Refrigerant vapor passes from rectifier 68 through line 82 to condenser '12 to complete the refrigeration cycle.

While I have described a preferred embodiment of my invention, it is to be understood the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

I claim:

1. An aqua-ammonia absorption refrigeration machine having a generator, a condenser, an absorber and an evaporator connected to provide refrigeration,

an electrical control circuit including an ammonia sensor associated with said machine to control the operation thereof, said ammonia sensor including a brass sensing element disposed in a position to sense an ammonia leak in said evaporator, said brass element forming an electrically conductive portion of said control circuit which corrodes rapidly in the presence of ammonia to open said electrical control circuit and shut off the machine.

2. An aqua-ammonia absorption refrigeration machine according to claim 1 further including means to stress said element to increase the corrosion rate thereof.

3. An aqua-ammonia absorption refrigeration machine according to claim 2 wherein said sensing element is a brass wire, and said means for stressing said element includes a spring.

4. An aqua-ammonia absorption refrigeration machine according to claim 3 wherein said ammonia sensor includes a housing having a central recess formed therein, said housing having two passageways extending therethrough parallel to the recess therein and on opposite sides thereof, said spring being disposed in the recess,

means adapted for engagement with said spring for movement axially within the recess, said brass wire being disposed within said housing having one end thereof in each passageway and fomiing a loop over said engagement means, the ends of said wire being suitably secured within the passageways so that said engagement means is held within the recess in said housing against said spring, said wire being stressed by said spring and said engagement means so that when said wire isexpo'sed to ammonia and is weakened thereby, said spring will exert sufficient force to break said wire to open said electrical control circuit. 

1. An aqua-ammonia absorption refrigeration machine having a generator, a condenser, an absorber and an evaporator connected to provide refrigeration, an electrical control circuit including an ammonia sensor associated with said machine to control the operation thereof, said ammonia sensor including a brass sensing element disposed in a position to sense an ammonia leak in said evaporator, said brass element forming an electrically conductive portion of said control circuit which corrodes rapidly in the presence of ammonia to open said electrical control circuit and shut off the machine.
 2. An aqua-ammonia absorption refrigeration machine according to claim 1 further including means to stress said element to increase the corrosion rate thereof.
 3. An aqua-ammonia absorption refrigeration machine according to claim 2 wherein said sensing element is a brass wire, and said means for stressing said element includes a spring.
 4. An aqua-ammonia absorption refrigeration machine according to claim 3 wherein said ammonia sensor includes a housing having a central recess formed therein, said housing having two passageways extEnding therethrough parallel to the recess therein and on opposite sides thereof, said spring being disposed in the recess, means adapted for engagement with said spring for movement axially within the recess, said brass wire being disposed within said housing having one end thereof in each passageway and forming a loop over said engagement means, the ends of said wire being suitably secured within the passageways so that said engagement means is held within the recess in said housing against said spring, said wire being stressed by said spring and said engagement means so that when said wire is exposed to ammonia and is weakened thereby, said spring will exert sufficient force to break said wire to open said electrical control circuit. 